Surgical Correction of Torticollis Due to Agenesis of the Sternocleidomastoid: Case Study and Review.

Unilateral agenesis of the sternocleidomastoid (SCM) muscle is a rare phenomenon known to cause torticollis. There have been around 12 reported instances of SCM agenesis in the literature; in almost every case, torticollis was easily resolved nonsurgically with stretching and physical therapy. We report the case of a 6-year-old boy with severe torticollis due to unilateral SCM absence who underwent the surgical release of the contralateral SCM. To our knowledge, this is the first time a surgical release of the SCM was performed to correct torticollis associated with agenesis of the SCM.